Self-passivating Cu laser fuse

ABSTRACT

In an integrated circuit structure, the improvement comprising a self-passivating Cu-laser fuse characterized by resistance to oxidation and corrosion and improved adhesion in the interface between Cu and metallization lines and Cu and a dielectric cap subsequent to blowing the fuse by an energizing laser, the fuse comprising: 
     a metallization-line; 
     a liner separating the metallization line and a combination Cu-alloy seed layer and a pure Cu layer; 
     a dielectric surrounding the liner; and 
     a dielectric cap disposed over the surrounding dielectric, the liner and the combination Cu-alloy seed layer and pure Cu layer; the laser fuse being characterized after Laser energizing by passivation areas: 
     a) on the open Cu-fuse surface; and 
     b) in the interfaces between: 
     (i) the Cu-alloy seed layer and the liners and dielectric; and 
     (ii) between the pure Cu layer and the dielectric cap.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to self-passivating Cu laser fuses in anintegrated circuit or semiconductor device prepared by using Cu-alloysand annealing steps to provide Cu/low k integration schemes. Theseself-passivating Cu materials may also be used in Cu-to-Cu wire bonding.

2. Description of Related Art

In the art of laser fuses used as a portion of a semiconductor, thestate of the art is to use fuses of pure Cu; however, under this usagethe fuses are very sensitive to corrosion and oxidation as soon as thefuse is blown and the Cu is exposed to the atmosphere.

Nevertheless, in Cu-oxide integration schemes it is possible to getaround the aforementioned problem by innovative layout and design of thefuse (i.e. ending the fuse on top of W-bars and containing the Cuoxidation and corrosion in the Cu-features of the fuse).

This innovative layout and design approach is not feasible in Cu/low kmetallizations because of the high diffusivity of moisture and oxygen inthe typical low k field, for the reason that corrosion of the Cu fusewould proceed to adjacent Cu wirings due to poor liner integrity at thesidewalls of damascene features.

An alternative to the state of art approach in lieu of using pure Cu(which is very sensitive to corrosion plus oxidation as soon as the fuseis blown and Cu is exposed to the atmosphere), is the use of Al-fuses ontop of a Cu-metallization. However, this alternative approach isexpensive because it requires many additional steps in the manufacturingprocess.

U.S. Pat. No. 5,747,868 disclose a laser fusible link structure forsemiconductor devices comprising: a plurality of laser fusible links,each fusible link having a link length extending along a lengthdirection and a link width extending along a width direction; a firstdielectric layer conformally covering the laser fusible links; for eachlaser fusible link, an etch mask member disposed on the first dielectriclayer vertically aligned over its respective laser fusible link, eachetch mask member having a mask length extending in the length directionand a mask width extending in the width direction, the mask width beinggreater than or equal to the link width of its respective fusible linkand less than or equal to the minimum spot size of the laser; and theetch mask members extending beyond the window perimeter in the lengthdirection, the window perimeter extending beyond the etch mask membersin the width direction.

A laser fuse structure formed over an active circuitry of an integratedcircuit is disclosed in U.S. Pat. No. 5,986,319. The integrated circuitcomprises: active circuitry; a first insulating layer, the firstinsulating layer overlying the active circuitry; a metal fuse layerabove the first insulating layer, the metal fuse layer including atleast one fuse, the at least one fuse being a radiant-energyconfigurable fuse having a location such that the beam area of theradiant energy used to configure the at least one fuse overlaps theactive circuitry; a first multi-metal protective layer underneath the atleast one fuse, the first multi-metal protective layer sufficientlylarge to shield the active circuitry from the radiant energy notdirectly impinging upon the at least one fuse; a second insulating layerbetween the first multi-metal protective layer, and the at least onefuse; a second multi-metal protective layer underneath the firstmulti-metal protective layer, the first and second multi-metalprotective layers being sufficiently large to shield the activecircuitry from the radiant energy not directly impinging on the at leastone fuse; and a third insulating layer on the second multi-metalprotective layer, the third insulating layer disposed between the firstand second multi-metal protective layer.

U.S. Pat. No. 5,622,608 disclose a process for preparing an oxidationresistant, electrically conductive Cu layer on a substrate, andsubsequently annealing. The annealing step is believed to provide ametal oxide layer at the surface of the Cu layer upon annealing.

Passivated Cu conductive layers for microelectronic applications isdisclosed in U.S. Pat. No. 6,057,223, in which the Cu conductors formedare included as a component in a microelectronic device. The conductoris formed by forming a metal layer on the surface of a microelectronicsubstrate, forming a Cu layer on the metal layer, and annealing themetal and Cu layers. The annealing step is believed to diffuse some ofthe metal layer through the Cu layer to the surface where the diffusedmetal forms a protective metal oxide at the surEace of the Cu layer. Asa result, the metal oxide layer passivates the Cu layer.

In the semiconductor manufacturing art in which a laser fuse is made aportion of the semiconductor as an effective way to alter the operationof semiconductor devices after the device has been fabricated to provideimplementing redundancy schemes to replace defective portions of anintegrated circuit with redundant portions, there is a need in the caseof Cu laser fuses to prevent corrosion and oxidation as soon as the fuseis blown by laser energy and the Cu is exposed to the atmosphere.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a semiconductor devicewith a laser fuse portion comprising copper, in which the copper is notsusceptible to corrosion as soon as the fuse is blown during energizingby a laser.

Another object of the present invention is to provide a semiconductordevice with a laser fuse portion comprising copper, in which the copperis not subject to oxidation as soon as the fuse is blown by laser energyand the copper is exposed to the atmosphere.

A further object of the present invention is to provide a semiconductordevice with a laser fuse portion comprising copper without the need ofending the fuse on top of W-bars to contain Cu oxidation and corrosionin the Cu-features, when the fuse is blown by laser energy and Cu isexposed to the atmosphere.

A still further object of the present invention is to provide asemiconductor device with a laser fuse portion that comprises Cu/low kmetallizations in which corrosion of the Cu-fuse would normally proceedto adjacent Cu wirings (due to poor liner integrity at the sidewalls ofdamascene features) are made to resist corrosion and oxidation of theCu-fuse upon subjection to laser energy.

In accordance with the invention, prevention of corrosion and oxidationof the Cu laser fuse portion of a semiconductor as soon as the fuse isblown by laser energy is avoided by passivating a Cu-alloy between theliner and a dielectric cap subsequent to an application of laser energyto break or blow the fuse, by an annealing step to provide aself-passivating dopant rich layer on top of the open Cu-laser fuse areaand at the Cu-interfaces to surrounding metallic liners and dielectricdiffusion barriers.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 is drawing of a semiconductor device comprising a laser fusecomponent comprising a copper alloy.

FIG. 2 shows a semiconductor device of the invention comprising apassivated laser fuse component formed by subjecting Cu-alloy of theblown fuse to an annealing step to form a self-passivated Cu-surface andinterface to the metal liner and dielectric cap layer to preventcorrosion and oxidation.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In general, in the context of the invention, the laser fuse componentcomprising Cu of the semiconductor device is prepared by the followingprocess sequence: 1) patterning a (Dual-) Damascene structure in thedielectric to form a fuse; 2) depositing a metallic liner (PVD, CVD,electroless, etc.; this step may be optional by using the optimumCu-alloy); 3) depositing of a seed-layer of a Cu-alloy for final Cu-fill(PVD or CVD or other art known methods); 4) filling the damascenestructure with pure Cu (electroplating, CVD, electroless, PVD or otherart known methods); 5) pre-CMP annealing at low temperatures (<200° C.),to form a low resistive Cu film (larger Cu grains); however, theout-diffusion of the dopants in the Cu-alloy should still be suppressedat this point; 6) Cu-CMP to remove the Cu-overfill, followed by theliner CMP; 7) depositing of a dielectric cap layer (Cu diffusionbarrier, Si-Nitride, Blok or other art known method); 8) depositing afinal passivation layer (oxide/nitride or combinations) or otherdielectric layers known in the art; 9) depositing a polyimide orphoto-sensitive polyimide (PSP) layer (optional); 10) thinning of thedielectric cap layer or final passivation layer on top of the laser fuseby using known lithographic+etch processes; 11) laser fusing of themetal fuse (during the fusing process a crater is formed in the nearsurrounding area of the blown Cu fuse; the two ends of the Cu fuse arenow exposed to the atmosphere); and 12) annealing the bonded chips attemperatures between 250° C.-450° C. (in inert atmosphere) to form aself-passivating layer on the open Cu-fuse surface and also on theinterfaces to metallic liners and/or dielectric cap layers; theself-passivating layer protecting the open ends and the embedded partsof the Cu fuse from oxidation and corrosion.

Reference is now made to FIG. 1, which shows a semiconductor devicecomprising a Cu-laser-fuse 10, composed of a Cu-alloy 11 disposed abovea liner 12, which is bounded by a metal-line 13. The Cu-laser-fuse isdisposed between a dielectric 14 and a dielectric cap 15. The intendedlaser energy 16 for blowing the fuse has not yet been applied.

As may be seen from FIG. 2, after the Cu-alloy laser fuse is blown bythe energizing laser, a fuse crater 20 is formed, and thereafter ananneal is performed to create a self-passivating dopant rich layer ontop of the opened Cu-laser fuse areas and at the Cu interfaces to thesurrounding metal-liners and dielectric diffusion barriers. Theself-passivated dopant rich Cu-interface to the surrounding metal-linerand dielectric diffusion barriers is designated by the X's, and withinthe confines of the borders defined by the X's, is the Cu 16. Thisdopant rich self-passivating layer is free from hillock structures andprotects the Cu from corrosion, oxidation and the outdiffusion of Cuinto semiconductor device areas.

In general, the Cu-alloys may be Cu—Al, Cu—Mg, Cu—Li, as well as otherwell-known Cu-alloys, and the concentration of the non-Cu dopingmaterial from the other component of the Cu-alloy will range from about0.1 to about 5.0% by weight of the Cu-alloy.

This self-passivating Cu-fuse is especially important when employed inCu/low k integration schemes and in Cu-to-Cu-wire bonding.

In the current state of the art where pure Cu is used, and wherein theCu is very susceptible to corrosion and oxidation as soon as the fuse isblown and copper is exposed to the atmosphere, the Cu-oxide integrationschemes may be circumvented or gotten around by utilizing a cleverlayout and design of the fuse (i.e. ending the fuse on top of W-bars andthereby containing the Cu oxidation and corrosion in the Cu-features ofthe fuse). However, this design around layout approach would not beavailable in Cu/low k-metallizations because of the high diffusivity ofmoisture and oxygen in the typical low k materials.

Further, in the typical Cu/low k-metallizations, the corrosion of theCu-fuse proceeds to adjacent Cu wirings, because of poor liner integrityat the sidewalls of damascene features.

Although certain representative embodiments and details have been shownfor purposes of illustrating the preferred embodiments of the invention,it will be apparent to those skilled in the art that various changes inthe invention disclosed may be made without departing from the scope ofthe invention, which is defined in the appended claims.

What is claimed is:
 1. In an integrated circuit structure, the improvement comprising a self-passivating Cu-laser fuse characterized by resistance to oxidation and corrosion and improved adhesion in the interface between Cu and metallization lines and Cu and a dielectric cap, subsequent to blowing the fuse by an energizing laser, said fuse comprising: a) a metallization-line; b) a liner separating said metallization line and a combination Cu-alloy seed layer and pure Cu layer; c) a dielectric surrounding said liner; and d) a dielectric cap disposed over said surrounding dielectric, said liner and said combination Cu-alloy seed layer and pure Cu layer; and e) a passivation layer of oxide, nitride or combinations of nitrides deposited on said cap layer that has been annealed at a temperature of from about 250° C. to about 450° C.; said laser fuse being characterized after laser energizing by passivation areas; f) on the open Cu-fuse surface; and g) in the interfaces between: (i) said Cu-alloy seed layer and said liners and dielectric; and (ii) between said pure Cu layer and said dielectric cap.
 2. The structure of claim 1 wherein dopant in said passivation areas is present in a range of from about 0.1 to about 5.0% by weight of said Cu-alloy.
 3. The structure of claim 2 wherein said Cu-alloy is selected from the group consisting of Cu—Al, Cu—Mg and Cu—Li.
 4. The structure of claim 3 wherein said Cu-alloy is Cu—Al.
 5. The structure of claim 3 wherein said Cu-alloy is Cu—Mg.
 6. The structure of claim 3 wherein said Cu-alloy is Cu—Li. 